A colony of dogs bred from parents with systemic lupus erythematosus (SLE) is under continous study. Cells and tissues from dogs and humans with SLE are analyzed for the presence of structural proteins of C-type RNA viruses. Antibodies to these viral proteins are sought in the serum. Analysis of the segregation of genes specifying C-type RNA viruses and autoimmunization NZB mice is continuing. BIBLIOGRAPHIC REFERENCES: Schwartz, Robert S.: Viruses and systemic lupus erythematosus. New England J. Med., 293:132-136, 1975. Schwartz, Robert S.: Autoimmunity, Malignant Disease and Viruses. In: Immunological Aspects of Neoplasia. Baltimore: Williams and Wilkins Co., 1975, pp. 243-252.